Buildings, such as homes, office buildings, warehouses, factories, and the like, often use load control systems for controlling electrical loads. Examples of electrical loads include electric lights, motorized window treatments, fans, and other such energy-consuming devices. FIG. 1 depicts such a load control system 10 in an example office building 11.
The load control system 10 may include one or more individual systems 12a-d. Depicted are three offices 14a-c and one conference room 14d—each room having its own individual system 12a-d. Each individual system 12a-d may include at least one load control device, for example, a wall-mounted dimmer switch 26, which may control an overhead light 18. The dimmer switch 24 may be responsive to an occupancy sensor 20. Specifically, the occupancy sensor 20 may detect when someone enters the room and then send a control signal to the dimmer switch 24. The dimmer switch 24, in response to the control signal, may turn on the overhead light 18. Similarly, the dimmer switch 24 may also be responsive to a light sensor (not shown) for dimming the light based on how much daylight is present. The load control system 10 may also comprise a motorized window treatment 22 that may be responsive to the light sensor. The dimmer switch 24, the occupancy sensor 20, the light sensor, and the motorized window treatment 22 may communicate wirelessly.
Because load control system 10 includes individually-operating systems 12a-d, the control devices of one individual system do not control the control devices of another individual system. Likewise, the control devices of one individual system do not respond to command signals from control devices of another individual system. For example, the occupancy sensor 20 in the office 14c adjacent to the conference room 14d would not control a dimmer switch 24 in the conference room 14d. And, the dimmer switch 24 in the conference room 12d would not respond to a control signal from the occupancy sensor 20 in the office 14c next door.
Having individual systems 12a-d in the rooms 14a-d is useful to the occupants of the building 11. The individual systems 12a-d are relatively easy to install. For example, the individual systems 12a-d can be installed and tested room-by-room, often done in parallel with multiple installers. The individual systems 12a-d are relatively easy to maintain. Changes in one individual system can made without affecting other systems. The individual systems 12a-d allow the load control system 10 to be somewhat flexible, since additional individual systems can be added to the building to allow for staged installations and growth over time. For example, the occupant of an office building may wish to install motorized window treatments in conference rooms first before installing them in individual offices. Similarly, the operator may wish to install occupancy sensors in the restrooms and storage rooms before rolling them out to the rest of the building.
However, there is a major drawback to using independently-operating systems 12a-d in the building 11—no system-wide control and management. Because the independently-operating systems 102a-d are completely independent, there is no mechanism for them to act in a coordinated way across the system as a whole. For example, demand response and whole-building timeclock functions are two popular and useful system-wide controls. An example demand response is when a load control system makes system-wide adjustment, such as reducing total electricity consumption, based on an indication from the electric utility—often when demand on the electric utility is the greatest. A whole-building timeclock function may include, for example, adjusting all of the lights in one mode during the day and another mode afterhours. Because these independently-operating systems 12a-d shown in FIG. 1 operate completely independently of each other, there is no mechanism for adjusting all of the independent units together in response to an indication from the electric utility or in response to a single time-clock. These beneficial system-wide capabilities are not available to a building with a load control system having conventional independent units 12a-d. 
Accordingly, there is a need for a load control system that provides the benefits of conventional independent units 102a-d, as well as, enables system-wide functionality, such as demand response and whole-building time clock functions.